Chain stoppers are commonly used in offshore mooring applications, such as for termination of mooring lines and hawsers to floating units and vessels. A chain stopper is usually used together with a mooring winch for unloading the mooring winch during regular operations. This is beneficial for the winch as well as for the chain itself.
Chain stoppers are usually operated manually, either directly or indirectly. Indirectly means by manually operating equipment, such as hydraulic equipment, adapted to engage a locking function for locking the chain by means of the chain stopper. Most chain stoppers are provided above sea level, typically on a vessel or floating unit which is being moored. This implies that chains are running over bends, such as in fairleads or bending shoes, under high tension, which is undesirable due to wear and fatigue of the chain. The fatigue problem is particularly pronounced in mooring of permanent offshore structures, as the same or a few chain links are constantly being subject to considerable stresses and wear. It is a further drawback of the prior art chain stoppers that the part or portion of the chain stopper engaging one or more chain links is not adapted to handle forces acting on the chain in a gentle way, thus contributing to increased wear.
A few known chain stoppers are semi-automatic, in that the chain stoppers may automatically engage the chain as soon as the tension from the winch is being reduced or is coming to a stop. Such semi-automatic chain stoppers typically use a pin or other stopping means biased by means of springs, or the like, in order to engage the chain. The semi-automatic chain stoppers tend to be rather complicated in use and not as reliable as is typically required in offshore mooring applications. The semi-automatic stoppers also tend to induce a lot of additional stresses and wear on the chain links being engaged.